If the roads are really iffy, I'm thinking that you won't see much of an improvement with anything smaller than a 32mm tire and a more forgiving frame geometry. A cyclocross bike would likely be a good choice - espeically given your comfort with regular drop bars. It would be easy to install mustache bars or a compact drop bar (or even flared "dirt drop" bars) on a cyclocross bike, because the bar diameter would be compatible.
If you really want an IGH (I can't blame you - I like IGH's) some other alternatives to the Swobo would be:
MEC Hold Steady (MEC will ship to the USA from Canada). My wife has one of these and loves it
Giant Seek
Civia
Kingfield or
Hyland
Scott
Venture 30 (Step-through style)
Scott
Sub10
To name a few.
If you really want something fun, you could build up a
Soma Buena Vista with a Nexus 8 speed for under $1500 if you kept the parts mix reasonable. The mixte will have a longer effective top tube, so you'd have to keep that in mind when selecting stem and bars.